This is one of those topics which, due to the nature of the question, means you'll find a startling array of historiography on the topic. We have several older answers on the subreddit which over angles on the question, including this one by /u/ThanklessAmputation, or this one by /u/a_soporific with some important weighing in from /u/true_new_troll, but I would certainly stay away from calling any of them the final word so hope others can weigh in further.

/u/Lukeintheskywith has previously answered Why was cocaine so widely used in the 70s and 80s?

There's a very good, emerging body of scholarship on this issue by historians such as Donna Murch that both critiques and nuances the Webb-era assessment of crack, the CIA, mass incarceration, and so on. If you can get hold of it, her article “Crack in Los Angeles: Militarization, Crisis, and the Late Twentieth Century War on Drugs,” Journal of American History, July 2015 is excellent on the wider context of militarised policing, the carceral state, and Black responses to the aforementioned. As far as I'm aware, Prof. Murch's next major book will be assessing this within the wider context of mass incarceration, race, etc. On Webb, I'd recommend Kathryn Olmsted's 2009 work Real Enemies: Conspiracy Theories and American Democracy, World War 1 to 9/11, in particular the chapter 'Trust No One: Conspiracies and Conspiracy Theories from the 1970s to the 1990s'.

Hope this helps.

Malcolm